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3 pages, 179 KiB

Open AccessEditorial

Energy Geotechnics and Geostructures

by Peng Pei and Faqiang Su

Energies 2023, 16(8), 3534; https://doi.org/10.3390/en16083534 - 19 Apr 2023

Viewed by 870

Abstract

Continuous global economic and population growth has driven the ever-increasing demand for energy [...] Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

Research

Jump to: Editorial

11 pages, 2086 KiB

Open AccessArticle

Study on Calculation Method of Heat Exchange Capacity and Thermal Properties of Buried Pipes in the Fractured Rock Mass-Taking a Project in Carbonate Rock Area as an Example

by Lin Wang, Yonglin Ren, Fengqiang Deng, Yiqiang Zhang and Yan Qiu

Energies 2023, 16(2), 774; https://doi.org/10.3390/en16020774 - 9 Jan 2023

Cited by 3 | Viewed by 958

Abstract

Fractures are developed in carbonate rock areas, and the fracture water flow significantly influences the heat exchange between buried pipes and the rock mass by induing heat convection, providing the carbonate rock area a strong heat exchange capacity and preferable conditions for shallow [...] Read more.

Fractures are developed in carbonate rock areas, and the fracture water flow significantly influences the heat exchange between buried pipes and the rock mass by induing heat convection, providing the carbonate rock area a strong heat exchange capacity and preferable conditions for shallow geothermal development and utilization. In this paper, the calculation method of heat exchange capacity of buried pipes based on fracture distribution characteristics is proposed and deduced, featuring such advantages as quick speed and low cost. Taking an actual project in carbonate rock area as an example, the heat exchange capacity of buried pipes was obtained by the following two methods: in-situ thermal response test and calculation based on fracture distribution characteristics. In the thermal response test, the initial ground temperatures of the two test holes were 15.18 °C and 12.72 °C. By fitting the linear equation of time and average temperature with a linear thermal source model, the heat exchange capacities were 57.21 W/m and 58.22 W/m, the thermal conductivities were 3.56 W/(m·K) and 2.32 W/(m·K), the thermal diffusivities were 1.71 × 10⁻⁶ m²/s and 1.12 × 10⁻⁶ m²/s, and the volume specific heat capacity was 2.08 × 10⁶ J (m³·K). The test results indicated that the thermal property parameters of rock and soil mass were higher than those of other areas, with obvious wide-range distribution characteristics. Through the statistical analysis of outcrop fracture characteristics, combined with the cube law to calculate the fracture water flow and convective heat transfer, an alternative method for the calculation and optimization of buried pipe heat transfer in fractured rock mass area is also proposed in this paper. According to the measured fracture distribution characteristics of the field outcrop, the heat exchange capacities of the two holes were 57.26 W/m and 58.56 W/m, which were basically consistent with the thermal response test values and verified the reliability of the calculation method of heat exchange capacity of buried pipes based on fracture distribution characteristics. Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

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16 pages, 2769 KiB

Open AccessArticle

Feasibility Study of Construction of Pumped Storage Power Station Using Abandoned Mines: A Case Study of the Shitai Mine

by Xin Lyu, Ke Yang, Juejing Fang, Jinzhou Tang and Yu Wang

Energies 2023, 16(1), 314; https://doi.org/10.3390/en16010314 - 27 Dec 2022

Cited by 12 | Viewed by 2606

Abstract

Due to the proposal of China’s carbon neutrality target, the traditional fossil energy industry continues to decline, and the proportion of new energy continues to increase. New energy power systems have high requirements for peak shaving and energy storage, but China’s current energy [...] Read more.

Due to the proposal of China’s carbon neutrality target, the traditional fossil energy industry continues to decline, and the proportion of new energy continues to increase. New energy power systems have high requirements for peak shaving and energy storage, but China’s current energy storage facilities are seriously insufficient in number and scale. The unique features of abandoned mines offer considerable potential for the construction of large-scale pumped storage power stations. Several countries have reported the conversion of abandoned mines to pumped storage plants, and a pilot project for the conversion of an underground reservoir group has been formalized in China. A feasibility study that considered the natural conditions, mine conditions, safety conditions, and economic benefits revealed that the construction of pumped storage power stations using abandoned mines could ameliorate several economic, ecological, and social problems, including resource utilization, ecological restoration, and population resettlement. The construction of pumped storage power stations using abandoned mines not only utilizes underground space with no mining value (reduced cost and construction period), but also improves the peak-load regulation and energy storage urgently needed for the development of power grid systems. Combined with the underground space and surface water resources of the Shitai Mine in Anhui, China, a plan for the construction of a pumped storage power station was proposed. The challenges faced by the current project were evaluated, further research suggested, and demonstration projects established in order to help achieve carbon peaking and carbon neutrality goals. Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

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14 pages, 1192 KiB

Open AccessFeature PaperArticle

Development of a Weighting Procedure for Geomechanical Risk Assessment

by Ali Mortazavi and Nursultan Kuzembayev

Energies 2022, 15(18), 6517; https://doi.org/10.3390/en15186517 - 6 Sep 2022

Cited by 1 | Viewed by 1267

Abstract

Underground mining is one of the riskiest industries. It is well established that the investigation of geomechanical parameters at the design stage of an underground mine provides the approximate rock mass characteristics, which are associated with some risks in the design. From a [...] Read more.

Underground mining is one of the riskiest industries. It is well established that the investigation of geomechanical parameters at the design stage of an underground mine provides the approximate rock mass characteristics, which are associated with some risks in the design. From a realistic risk assessment point of view, it is essential to classify risky design parameters as relevant to risk groups and determine a suitable weighting strategy for risk-prone elements aiming at risk assessment. Therefore, a realistic weighting procedure is an essential step in making realistic design decisions to increase the safety of mining operations and economic vitality. This study aimed to develop a realistic weighting procedure to assess and compare various geomechanical parameters that pose a risk to opening stability. In this research, sub-level stoping mining methods, which are commonly used in the Kazakhstan mining industry, were selected to test the developed weighting algorithm. In this study, the risk-prone geomechanical parameters for the chosen mining method were defined, and a weighting procedure was developed using the Fuzzy Analytic Hierarchy Process (FAHP) method. The proposed methodology was verified against available data from the Ridder–Sokolny underground mine, and the analysis results showed good agreement with actual observations in the mine. The obtained preliminary results show that FAHP is a reliable method for weighting geomechanical parameters and can be used as an input in any geomechanical risk assessment practice. Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

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13 pages, 4113 KiB

Open AccessArticle

Research on the Application of Fracture Water to Mitigate the Thermal Imbalance of a Rock Mass Associated with the Operation of Ground-Coupled Heat Pumps

by Tingting Luo, Peng Pei, Jianan Wu, Chen Wang and Long Tang

Energies 2022, 15(17), 6385; https://doi.org/10.3390/en15176385 - 1 Sep 2022

Cited by 1 | Viewed by 1042

Abstract

Shallow geothermal energy is a clean and effective form of energy that can overcome the problems associated with the depletion of carbon-based energy carbon emissions. Due to the special hydrogeological conditions in karst regions, the heat transfer between heat exchange boreholes and the [...] Read more.

Shallow geothermal energy is a clean and effective form of energy that can overcome the problems associated with the depletion of carbon-based energy carbon emissions. Due to the special hydrogeological conditions in karst regions, the heat transfer between heat exchange boreholes and the ground formation is a complicated, multi-physical process. The abundant groundwater flow plays an important role in the heat transfer process, and even presents an opportunity to mitigate the heat imbalance during the long term operation of ground-coupled heat pumps (GCHP). In this study, both laboratorial experiments and numerical simulations were performed to analyze the mechanism that shows how fracture water impacts on heat capacity and the thermal imbalance of the energy storage rock mass. The results showed that the overall temperature fluctuation of the rock mass was reduced by the fracture water, and the temperature curve with time became gentler, which means in practice that the heat imbalance in the rock mass could be delayed. However, the temperature contour map showed that the impact of the fracture water flow was constrained in the nearby areas and decreased obviously with distance. The temperature field was also dragged along the direction of the fracture water flow. During the shutdown period, the fracture water significantly enhanced the thermal recovery ability of the rock mass. The results will assist in further understanding the mechanism of heat transfer and energy balance in a rock mass with fracture water flow. It is proposed that the U pipes should be located at zones with abundant fracture water if the construction condition permits. U pipes that are near the fractures should share more of the load or a denser layout could be possible as their heat transfer capacity is improved by the water flow. Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

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16 pages, 7221 KiB

Open AccessArticle

Fracture Distribution Characteristics in Goaf and Prevention and Control of Spontaneous Combustion of Remained Coal under the Influence of Gob-Side Entry Retaining Roadway

by Jianguo Zhang, Wen Wang, Yanhe Li, Huamin Li, Guangjie Zhang and Yiheng Wu

Energies 2022, 15(13), 4778; https://doi.org/10.3390/en15134778 - 29 Jun 2022

Cited by 5 | Viewed by 1131

Abstract

Based on the ventilation characteristics of the gob-side entry retaining face, a mathematical model of spontaneous combustion in the gob-side entry retaining face is established. From the overburden caving of the goaf along the goaf retaining roadway, the development characteristics of rock strata [...] Read more.

Based on the ventilation characteristics of the gob-side entry retaining face, a mathematical model of spontaneous combustion in the gob-side entry retaining face is established. From the overburden caving of the goaf along the goaf retaining roadway, the development characteristics of rock strata and residual coal fissures in the goaf are summarized and analyzed. In addition, by using numerical simulation software, the effects of normal mining period, goaf retaining roadway as return air roadway, air leakage prevention, and nitrogen injection measures in goaf on spontaneous combustion in goaf are studied, and the distribution characteristics of flow field, oxygen concentration field and temperature field in goaf are obtained. The results show that the mining of the Geng 20 working face has a significant impact on the Geng 19 coal seam. The Geng 19 coal seam is in the range of fracture zone, and the fracture is well developed. Furthermore, the permeability coefficient of the Geng 19 coal seam increases sharply, air leakage in the goaf is increased along the goaf retaining roadway, and the range of oxygen concentration is enlarged, which results in a temperature rise in the goaf. Therefore, air leakage measures are proposed along the goaf to inject 900 m³/h of nitrogen into the goaf, which can prevent the spontaneous combustion of coal left over in the goaf. In addition, according to the characteristics of fracture development and numerical simulation of spontaneous combustion in goaf under the goaf retaining roadway, the hierarchical prevention, control, and fire extinguishing technology system of the goaf retaining roadway is constructed. Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

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15 pages, 4929 KiB

Open AccessArticle

Research on the Mobile Refrigeration System at a High Temperature Working Face of an Underground Mine

by Jielin Li, Xiaoli Yu, Chonghong Huang and Keping Zhou

Energies 2022, 15(11), 4035; https://doi.org/10.3390/en15114035 - 31 May 2022

Cited by 6 | Viewed by 1359

Abstract

With an increase in mining depth, the problem of heat damage in metal mine working face has become increasingly prominent. In order to effectively reduce the temperature of the working face and provide a comfortable working environment for the miners, based on the [...] Read more.

With an increase in mining depth, the problem of heat damage in metal mine working face has become increasingly prominent. In order to effectively reduce the temperature of the working face and provide a comfortable working environment for the miners, based on the concept of “cooling on demand”, a mobile refrigeration system for high-temperature working face was designed, and a field test was carried out in Dahongshan Copper Mine, Yunnan Province. At the same time, based on the experimental conditions, the parameter optimization research of the mobile refrigeration system was carried out. The results showed that: (1) The mobile refrigeration system could reduce the wet bulb temperature of the working face at the test site to below 30 °C, which is in line with the “Safety Regulations for Metal and Non-Metallic Mines” (GB16423-2020); (2) when the diameter of the air supply pipe was 600 mm and the air supply velocity was 12 m/s, the target cooling area could meet the continuous operation requirements stipulated in the “Safety Regulations for Metal and Non-metallic Mines” in China; (3) for every 2 °C decrease in supply air temperature, the average wet bulb temperature in the target cooling area decreased by 0.9 °C; (4) for every 10% decrease in supply air humidity, the wet bulb temperature and relative humidity in the target cooling area decreased by 0.76 °C and 4.38% on average, respectively. The research results provide new ideas and methods for the prevention and control of heat damage in metal mines. Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

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17 pages, 5969 KiB

Open AccessArticle

Investigation of the Bearing Characteristics of Bolts on a Coal–Rock Combined Anchor Body under Different Pull-Out Rates

by Pandong Zhang, Lin Gao, Xinyu Zhan, Pengze Liu, Xiangtao Kang, Zhenqian Ma, Yongyin Wang, Ping Liu and Sen Han

Energies 2022, 15(9), 3313; https://doi.org/10.3390/en15093313 - 2 May 2022

Cited by 4 | Viewed by 1510

Abstract

In order to reveal the influence of the pull-out rate on the load-bearing properties of the coal–rock combined anchor body, the mechanical properties and failure characteristics of a coal–rock combined anchor body under different pull-out rates (10, 20, 30, 40, 50 mm/min) were [...] Read more.

In order to reveal the influence of the pull-out rate on the load-bearing properties of the coal–rock combined anchor body, the mechanical properties and failure characteristics of a coal–rock combined anchor body under different pull-out rates (10, 20, 30, 40, 50 mm/min) were studied using the pull-out test and theoretical analysis. The results show that the bearing capacity of the bolt on the coal–rock combined anchor body improves under a dynamic load, but the load-bearing properties of the coal–rock combined anchor body are different from those of the full rock (coal) anchor body. With the increase in the pull-out rate, the maximum pull-out load of the bolt on the coal–rock combined anchor body increases first, then decreases, and finally tends to be stable. Under the condition of a low drawing rate, the bearing capacity of the coal–rock combined anchor system can be greatly improved, but when the pull-out rate exceeds 20 mm/min, the bearing capacity of the anchor system is reduced. The debonding process of the anchoring section of the coal–rock combined anchor body gradually expands from the beginning section of the anchor to the bottom of the borehole. The coal–rock combined anchor body undergoes time differential development of cracks, and the failure of the coal and rock mass occurs at different times. Its failure process can be divided into three stages: (1) the coal anchor and rock anchor act together; (2) the rock anchor acts alone; and (3) the coal anchor and rock anchor have residual action. Full article

(This article belongs to the Special Issue Energy Geotechnics and Geostructures)

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